1. Field of the Invention
The invention relates to a sensor system based on the retroreflection of a laser beam.
The goal of this sensor system is to create a retroflective surface for laser sensor applications (laser sensorics) based on retroreflection and polarization rotation. This design supplies a laser signal with sharp contours for interpretation, thereby permitting significantly superior fine high-resolution scanning.
2. The Prior Art
Sensor systems designed to create the retroreflection of a laser beam are known in the art. For example, German Patent 42 40 680 A1 discloses a method of producing structured microtriple-element or microtriplet reflecting surfaces. According to this method, the retroreflecting microtriple reflector elements are similar to cubes, have a diameter in the range of 0.002 and 0.8 mm, and are combined in groups of identical microtriple reflector elements, whereby the diameter of such groups is smaller than 7 mm and the reflecting surface is formed by at least two or more groups.
Japanese patent 6-273608, describes a reflector having high reflection efficiency by forming a multitude of cube corners, which are arranged in different sizes on the reflecting surface in a mixed configuration.
In the field of sensor technology, laser sensor systems based on retroreflection and polarization rotation are known as reflex light barriers. Such reflex light barriers, which operate with laser light and polarization filters, are employed with retroreflectors. These retroreflectors can come in the form of expensive glass triple reflectors or triplets ground in large sizes, concave mirrors made of metal, and conventional triple reflectors made of glass or plastic. The interruption of the retroreflected beam between the retroreflector and the emitter or the receiver is interpreted as a binary signal.
The sensor system is designed to perform a series of calculations with different applications. The distance is calculated by finding the time required for the retroreflected beam to return. At the present time, laser light is preferred to control spreading of the beam of light to obtain an energetically strong signal with sharp contours for evaluation.
In gas analysis, the change in the spectrum of the retroreflected beam occurring in the glass flow chamber is evaluated.
To avoid errors in the interpretation of the signal, the laser beam is often additionally polarized, pulsated, or limited to a defined light spectra.
It is important to create a retroreflected beam with the sharpest possible contours. In this way, it is possible to distinguish the signal interpretation to be distinguishable from outside light or undesirable reflection rays.
Such undesirable reflection rays form when observing glass bottles in a bottle filling plant. Likewise, reflections are occur on metal, paint or plastic surfaces, when observing packages in a package distribution system. These objects can be observed with sensors. In addition undesireable reflections can occur when monitoring conveyor installations with sensors, or when scanning motor vehicles with sensors in car wash installations.
This fine resolution of the reflex sensor system depends on whether the retroreflector receives a sharply contoured signal that cannot be confused with outside radiation.